1. Field of the Invention
This invention relates to a method to search songs by their melodies.
2. Description of the Related Art
In prior art, music search has been performed by searching some keywords, such as its title, lyrics, or the performers. However, if we remember songs by their melodies, or hear some music without knowing what it is, it is difficult to find this song with the prior methods.
In U.S. Pat. No. 6,121,530 [Sonoda, 1999], a web-based music search engine with melody input has been presented. It analyzes the whole database to find a threshold for adjacent pitch differences and another for span ratios, and then uses the thresholds to encode the pitch sequences into Up/Down/Equal category, and span sequences into Longer/Shorter/Equal. Finally, the encoded sequence from the query melody is compared with each sequence in the database to find the best match. However, the global thresholds might not best describe the melody contour of each song in the database. That is, melodies with relatively smaller pitch changes might be considered no change at all. This rough categorization leads to lots of false matches. Another problem is that if a note is missing in the input, or an extra note is added to it, the distance will be large due to misalignment of corresponding notes.
In U.S. Pat. No. 6,188,010, a comparison method by marking peaks and dips is invented. However, it also suffers from the note misalignment problem. Another problem is that note spans are not considered.
In U.S. Pat. No. 6,678,680, the note sequence is encoded into adjacent note differences and span ratios. The distance between the query and target is defined by the sum of the absolute differences between the two symbols from each coded sequence. This method also suffers from the note misalignment problem as the previous two. Moreover, when the duration information is encoded in the string, the distance calculated by the difference of two symbols does not correlate to the difference between two melodies successfully.